Au where Shiro and Allura are immortals and trying to break into a museum to get their age old shit back and Lance is the security guard trying to shoo them away (no Shiro and Allura are not working together and in fact they didn't even know the other exist)
i must say non-canon aus are not always my jam but the vibes here are. immaculate. 👀
though i will concede to my bias and nudge this back into a semi-canon context and raise you: Allura wakes up from her sleep alone, decides to start trying to find the lions herself (maybe Coran wakes up too, maybe he's stuck in cryo, something something TBD). meanwhile Shiro was kidnapped by the Galra and made into a gladiator, just like in canon, but he is broken out by the rebels and/or the blade of marmora and recruited to also find voltron instead of being shipped immediately back to earth.
this all means the convergence happens a couple years down the line from the pilot in voltron, something something wibbly wobbly timey wimey. Lance has maybe advanced in his career at the Garrison, and instead of being a cadet is possibly a junior officer.
something something he's doing patrols/on guard duty one night, WHEN: shiro and allura, who have both separately been trying to find voltron, end up following leads back to Earth, converging on Blue at the same time. Lance is on a night shift and notices Something Fucking Weird in the sky, and being the over-eager and curious person we know he is, he decides to check it out himself.
something something they all end up in the cave, something something oh no they're hot. something something Blue chooses Lance. at some point Keith n Pidge n Hunk get involved, but the first bit is just Shiro + Allura rebel rivals, and Lance who is both actively Getting Up To Stuff but also all of this is kind of just happening to him, all at once. something something voltron, something something relationship development, something something and then they KISS.